There are two nuts on the fan speed adjusting motor shaft that need to be backed off a little. look behind that yoke that contoles the fan speed and you'll see them. Back those nuts up and you can probably get your fan speed up to 1200.
I had the exact same problem with my new belt. I could'nt get the speed out that I had with the old belt! I have a 1680 with a cross flow fan to and noticed that the belt ran all the way to the top side of the pulley. I then adjusted the "stop nuts" but it only caused the belt to ride out over the top of the pulley and still only had 1040 RPM. I did notice that the front side of the belt rode down in the drive pulley and the back side was all the way out. I thought it would seem to indicate to long a belt. Bummer, I guess I forgot to specify to the dealer that I had a crossflow fan!
On the top fan pulley (drive pulley),if your belt is not the same depth front side vs. rear side, check your bushings in your movable sheave. I would suspect they are tired, that fix might gain you the rpm you need.
By moveable sheave, are you referring to the top driver pulley or the bottom driven pulleyIJ Can the worn bushings be identified without disassembling or does it have to be taken apart to seeIJ Thanks!
I'm talking top pulley, outside sheave. 60 second job to check, just unpin the yoke that holds the throwout bearing on the front side, swing the yoke away, zip the bolt out on the end of the shaft, and slide the sheave off. A tired bushing will be obvious, inside of the sheave. Actually I think CNH wants you to buy the whole hub (the pulley unbolts from it),but if you know a good machinist he could put a bushing in it for you. Hope this helps.
You spelled it out very clearly, Jalopy! I'm sure there's a few people more then just me who appreciate what you just taught them. I usually am pretty good at figuring things out and doing my own repairs but it sure is nice to be able to "short-cut" my own learning curve and learn directly from someone with experience. Thanks!!
Yes, the last 100-200 rpm makes a difference in cleaning performance, especially on a 88 with the longer sieves. They need all the air they can get in certain conditions.
I realize this is a little late to chime in on this problem but a neighbor and myself have been through this issue. Since you have the crossflow fan, your dealer can sell you the pulleys from a 2388 which will then allow you to run your fan well over 1200 rpm. It is not recomended to run the fan over 1200 rpm due to mechanical failures but it is really nice to have the extra speed adjustment available so that your belt doesn't have to run so deep in the pulley causing it to heat and wear. Also as your belt wears you can keep your fan running over 1100 rpm.